Missing base class for all GTFS exceptions

[rorlic]

The GTFS exceptions in namespace GTFS.Exceptions all derive from the System.Exception class.

In order to log all issues that occur while reading a GTFS feed, one now needs to either catch the base class System.Exception or catch all exceptions from namespace GTFS.Exceptions explicitly.

Catching System.Exception is considered bad practice. The second approach is also not ideal because if a new GTFS exception is added, it will pass through.

IMHO, it is best to add an abstract base class (e.g. class GTFSExceptionBase) for all GTFS exceptions in namespace GTFS.Exceptions.

Ugly workaround for now:

        try
        {
            gtfsData.GtfsFeed = reader.Read(gtfsDirectorySource);
        }
        catch (Exception ex)
        {
            var type = ex.GetType();
            if (!type.FullName.StartsWith("GTFS.Exceptions"))
            {
                throw;
            }

            // TODO: add logging here
        }

[xivk]

Two things:

• The feed validation process needs to be reworked.
• Exceptions should only occur when reading the feed is impossible.

I agree that it would be better to have a base class. Feel free to submit a pull request, otherwise I'll try and do this next time I work on this.

[rorlic]

Added class GTFSExceptionBase, derived all exceptions currently in namespace GTFS.Exceptions from it and added unit test to ensure all exceptions derive from this base.